reduction in in-reservoir phosphorus concentration.
-1
a 30-percent reduction in in-reservoir phosphorus concentration
1.0 year
approaches the best possible reduction, even with unlimited dilution water.
It can also be seen from Figure 10 that in-reservoir concentration can
increase by adding dilution water when the counteracting effect of decreased
loss to sediments is considered.
Uttormark and Hutchins (1978) conclude that lakes with low flushing
In these cases,
rates are poor candidates for improvement through dilution.
in-reservoir phosphorus concentration could increase (see Figure 10, low
-1
unless the dilution water is essentially void of
flushing rates,
year
phosphorus.
If summer
The model used here does not account for internal loading.
internal phosphorus loading, a common phenomenon in many lakes and reservoirs,
is high, then there may be less reduction in concentration than expected.
Substantial empirical studies of dilution are greatly needed.
=
10
0.1
0.01
FLUSHING RATE BEFORE DILUTION
YEAR-'
Percent change in in-lake phosphorus concentration fol-
Figure
lowing dilution with water having a phosphorus
that
is 40 percent of the normal, undiluted inflow water (after
Uttormark and Hutchins 1978). (See text for explanation)
67
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